Before gasoline-electric hybrids made headlines, the VW turbo direct injection (or TDI) diesel was the undisputed king of fuel economy. Even with competition like the Prius, Civic Hybrid, and Insight, TDI powered Volkswagens often delivered the highest real-world mileage available from the showroom floor. Now, with federally mandated ultra low sulfur ‘clean’ diesel fuel available in the U.S., Volkswagen is set to market the next generation of high-mileage diesel technology in all 50 states.
Later this year, VW will launch its cleanest diesel ever in the form of the Jetta SportWagen. The new four-cylinder 2.0-liter TDI engine meets the most stringent Tier II/ Bin 5 emissions standards, with tailpipe emissions on par with clean gasoline engines. Interestingly, these standards are tougher than their European counterpart, the Euro-5 emission standard. Volkswagen hasn’t officially announced fuel economy estimates, but inside sources indicate that mileage will be 12 percent better than the previous generation TDI. Even with the more aggressive 2008 EPA test procedures, that should mean real-world fuel economy in the low-to-mid 40 mpg range. Hyper-mileage enthusiasts may be able to coax well over 50 mpg from the new powertrain.
The new 16-valve 2.0-liter TDI produces 140 horsepower and importantly 235 lbs-ft of torque. That generous torque launches the Jetta with authority and delivers strong performance under load and on long grades. VW is meeting the strict 50-state emissions standards without the aid of urea injection. Instead, internal engine modifications include unique cylinder pressure sensors that allow a new type of individual cylinder pressure based combustion control. The high-pressure injection pump, common rail fuel supply, and high pressure injectors have also been optimized along with the addition of dual high and low pressure exhaust gas recirculation systems. Exhaust after-treatment includes an oxidation catalytic converter, particulate filter, and a NOx trap.
Perhaps most impressive is what you don’t get with the new TDI. Quiet and smooth, the latest TDI gives few cues that you are driving a diesel. In fact, while idling next to a four cylinder economy car, the TDI was noticeably quieter. And of course, there is no tell-tale sooty smoke or diesel odor.
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